In this lesson your students will conduct a series of hands-on experiments that will help them to understand the role of lift in fixed-wing flight. Students will observe the flow of air and water around several surfaces and then consider the dynamics of airflow around an aircraft wing.

You may wish to begin the activity by telling your students that, although air is invisible to the human eye, it is made up of physical matter--real "stuff." This means that air exerts a force that helps to keep an airplane up in the air.

Tell your students that the experiments in this lesson will demonstrate what Swiss mathematician Daniel Bernoulli discovered in the early 1700s: When flowing air or water changes speed, its pressure also changes.

With each activity, ask your students to consider what is going on.

Is air slowing down or speeding up?

How might air pressure be changing?

How might the flow of air (and its changing pressure) help to keep an aircraft up in the air?

Direct your students to the Use Your Lips to Levitate" and
"Balloons That Boggle" activities (Activity 2A). What happens when air is blown over the paper or between the balloons? Ask students what they think causes the paper and balloons to move.

After your students have finished the activities, direct them to the "What's Going On? The Simple Explanation" section.(You may wish to have several students alternately read this section aloud.) Use the questions in the text as the basis for a class discussion. Be sure that students understand that air loses pressure when it speeds up.

Ask your students to begin the "Squeeze the Stream" activity (Activity 2B). Explain that this activity is more complex than the previous two activities and will require teamwork. (You may wish to have three or four experiments going simultaneously, so
that all students can observe the water movement firsthand.) Stress that although this experiment uses water, air flows in a similar manner.

Direct your students to the "What's Going On? The Advanced Explanation" section (Activity 2C). (You may wish to have several students alternately read this section to the class.)

Conclude the activity by reinforcing these important concepts:

1. Air speeds up as it moves around an object.
2. When air moves faster, its pressure drops and it pushes less.
3. When an airplane flies, air speeds up more above the wing than below it. As a result, the air above an airplane wing pushes less than the air below the wing. The higher pressure below the wing pushes the wing (and the airplane) up.